Figure 2.

c-Abl–mediated in vitro phosphorylation and characterization of Tau (pTau). Phosphorylation was performed for 4 h, which leads to a mixture of Tau phosphorylated on two to five residues. Characterization of the RP-HPLC purified Tau and the pTau mixtures by LC-MS (A), UPLC (B), and SDS-PAGE (C). D and E, tandem LC/MS/MS of RP-HPLC purified pTau following trypsin digestion and peptides enrichment using a TiO₂ resin. The analysis of the phosphopeptides was performed using the Scaffold version 4.0 (Proteome Software), and the number of phosphopeptides detected per phosphorylation site was reported as the spectral count (SP).